Techniques for detection and identification of substances are exploited nowadays in a variety of implementations aiming at detection of trace amounts of particular materials, such as, but not limited to, narcotics, explosives, toxic industrial chemicals and minerals (e.g., surface geochemical exploration, such as oil and gas exploration).
Some exemplary implementations of such substance detection techniques are disclosed in the following patent publications.
U.S. Pat. No. 5,859,375 describes a handheld sampling apparatus having a handle, a head connected to the handle and a mechanism for retaining a substrate on the head in a form of a flexible sheet, which is mounted so as to present a collection portion thereof for collection of a sample. The substrate is configured to be readily fitted into an inlet portion of an analyzer. The apparatus enables an area to be sampled quickly and efficiently, while keeping a user's hands away from the surface, which enables otherwise inaccessible areas to be sampled.
U.S. Pat. No. 6,642,513 discloses sample traps or wipes for a detection system for detecting contraband materials. The sample trap is formed from an open weave glass fabric coated with a thin layer of Teflon and roughened to cut through the surface of Teflon and to break some of the glass fibers. Alternatively, the sample trap is non-woven felt fabric made of high temperature polyamide fiber. The sample traps are used in a detector, such as an ion trap mobility spectrometer. The detector includes a desorber, which feeds dry air from a manifold above and below the sample trap through a series of holes along the mouth of the desorber. The dry air passes through the trap and purges out unwanted atmospheric constituents that could otherwise affect the performance of the detector. The purged air passes to the outside atmosphere, thus creating a dry curtain at the entry to the desorber.
US Patent publication No. 2001/039824 describes a vapor sensing device that is sufficiently small and lightweight to be handheld, and also modular so as to allow the device to be conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each vapor. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor. These chemically sensitive resistors can each be connected in series with a reference resistor, between a reference voltage and ground, such that an analog signal is established for each chemically sensitive resistor. The resulting analog signals are supplied to an analog-to-digital converter, to produce corresponding digital signals. These digital signals are appropriately analyzed for vapor identification.